This invention relates to couplings used for transmitting rotation from one shaft to another, and more particularly, to a coupling using an elastomeric belt or cushions with a retaining ring or sleeve used to keep the belt or cushions in place.
Various types of flexible couplings have been used for connecting one shaft to another. These couplings compensate for relatively minor degrees of shaft misalignment, which are normally encountered in manufacturing operations.
One type of prior art coupling uses two hubs, each hub having a plurality of projecting jaws extending from the hub face toward the other hub face. Such couplings, called jaw-type couplings, are sold by Lovejoy, Inc. of Downers Grove, Ill., the assignee of this application. The hubs are each mounted on one of the shafts. The jaws extending from each hub face are of a length so that they will be slightly separated from the other hub face when the coupling is assembled. The jaws, which are parallel to but overlap each other, are separated by spaces. An elastomeric element, often called a spider, occupies the plurality of spaces formed between adjacent jaws. Thus, the force from the jaws of the one hub is transmitted through the elastomeric element to the jaws of the other hub. These couplings operate with the elastomeric element in compression and have the characteristics of compactness, capable of transmitting large forces and continuing to transmit rotational forces even when the elastomeric element fails. This last characteristic can be an advantage or a shortcoming in that if the elastomeric element fails, the jaws of one hub strike the jaws of the other hub and continue to drive the driven shaft and any equipment to which it is connected. Thus, in an overload condition, the driven equipment is not protected by the coupling.
Another type of flexible coupling is illustrated in U.S. Pat. No. 5,139,460 by Hoyt, III et al., U.S. Pat. No. 6,142,878 to Barin and U.S. Pat. No. 6,159,102 to Barin et al. This type of coupling is similar to the previously described coupling in that both designs have a pair of hubs, each pair of hubs having extending jaws. The hubs are mounted on their respective shafts. However, the jaws on one hub are parallel to and aligned with the jaws on the other hub. A belt surrounds the hubs and fills in the spaces between adjacent pairs of jaws. In this design, the belt operates in shear.
Advantages of this type of design are that the belt provides for misalignment between the shafts; the belt transmits power uniformly; the belt provides damping; and if the belt fails, the driven equipment is protected, as it will essentially be disconnected from the drive shaft. Furthermore, this type of design allows the belt to be replaced without disassembling the hubs or moving the equipment connected to the shafts.
Another type of shear coupling is illustrated in U.S. Pat. No. 5,295,911 to Hoyt, III et al. This design illustrates jaws overlapping each other while using an elastomeric belt between overlapping jaws to transmit the torque. There is also shown a retaining ring surrounding the belt to keep the belt in place.
A problem arises in this coupling in that the retaining ring has a tendency to slip from its desired position of being centered on the belt. If the retaining ring slips off the belt, the belt will come loose and the coupling will disengage. One attempt at solving this problem has been to cut a groove or channel in the belt perpendicular to the edge of the belt. This is illustrated in U.S. Pat. No. 6,024,644 to Hoyt III et al. The solution was to cut another groove perpendicular to and intersecting the first groove, which extends a short distance in either direction around the circumference of the belt. There is a pin on the inside surface of the ring, which is received in the grooves. This design locks the pin in place when rotating in either direction.
Applicant has designed a new flexible coupling that is designed to operate in shear, in which the band or locking ring locks around the elastomeric belt without utilizing a circumferential groove cut into the belt as illustrated in the prior shear type couplings. In an alternate embodiment, the elastomeric belt is not used. Instead it is replaced with a plurality of cushions that are placed between the jaws. The cushions function in the same manner as the elastomeric belt to operate in shear. A retaining ring locks the cushions in place.
Accordingly, it is an object of the invention to provide a flexible coupling which operates in shear and utilizes a retaining ring about the elastomeric belt or cushions.
It is a related object to provide a shear type flexible coupling, which has a retaining ring securely, yet releasably, fastened to the elastomeric belt or cushions. Yet another object is to provide such an elastomeric belt or cushions and retaining ring which secures the retaining ring to the belt or cushions regardless of the direction of rotation of the hubs.
Still another object is to provide a retaining ring that locks around the elastomeric belt or cushions without requiring a circumferential groove to lock the retaining ring to the elastomeric belt or cushions. Related to this object is the object of providing an elastomeric belt or cushions that has raised portions or nubs on the edges of the elastomeric belt or cushions to lock the retaining ring in place. A related object is to provide an angled ramp on the edge of the belt or edge of the cushions that provides progressive resistance, similar to a screw thread.
The invention disclosed herein provides a shear-type flexible coupling in which the jaws on the hubs are in parallel alignment and spaced from each other. A flexible elastomeric belt or cushions fill the gaps between adjacent pairs of jaws. A retaining ring is mounted around the belt or cushions to keep the belt or cushions securely in place. The exterior of the belt surface has a groove cut axially on the outer surface of the belt from one edge of the belt to the other edge. There is a pair of raised projections or nubs on the edge of the belt, preferably on either side of the groove. A locating or locking pin on the inside of the retaining ring is slid along one of the perpendicular grooves until the pin exits the opposite end of the groove. The retaining ring is rotated so that the locking pin also rotates over the raised projection or nub. This locks the retaining ring in place regardless of the side from which the retaining ring is slid onto the belt or the direction of rotation of the coupling. In an alternate embodiment, the edges of the belt or cushions are formed as an angled ramp that provides progressive resistance to the pins to lock the retaining ring around the cushions.